Wafer-level Test and Burn-in (WLTBI) refers to the process of subjecting semiconductor devices to electrical testing and burn-in while they are still in wafer form. Burn-in is a temperature/bias reliability stress test used in detecting and screening out potential early life failures.
Test equipment for burn-in and other testing of electrical circuits generally comprise a connection arrangement for electrically connecting an electrical circuit to be tested, such as an integrated circuit on a wafer or test substrate, to a test probe circuit.
WLTBI usually employs a wafer prober to supply the necessary electrical excitation to all the die on the wafer through hundreds or thousands of ultrathin probing needles (mounted on a probe card) that land on the bond pads, balls, or bumps on the die. The wafer is generally placed on a chuck plate, and the probe card must be properly aligned to the wafer.
To maximize throughput and minimize per-wafer testing costs, multi-wafer testing has emerged as an important technique. This generally involves the loading of multiple wafers into cartridges for alignment or for transport to the testing station. Two current approaches in use for multi-wafer test are:    1. Multi-chuck probers: Standard wafer probers are modified to contain multiple chucks. The chucks share a common loading mechanism but operate independently during alignment and test. In general, the loading mechanisms may be largely automated and utilize Front Opening Unified Pods (FOUP's), which are described in http://en.wikipedia.org/wiki/FOUP. An issue with this method is that multi-chuck probers require that each stage contains all of the necessary optical, electrical, and mechanical hardware to perform the fine alignment of the wafer to the probe card, resulting in substantial added cost to the overall test cell due to the duplication of hardware. Further, current multi-chuck probers scale in the horizontal dimension, taking up additional floor space for each added wafer.            2. Manual-insertion Cartridge-based Test Cell: Wafers are loaded into cartridges and aligned at a separate alignment station located on the test floor. The alignment of the probe card to the wafer is done at the alignment station after the cartridge is assembled into a single unit. This alignment is done by moving the probe card relative to the fixed wafer. Operators move the cartridges from the alignment station to the test cell and insert them into the testing rack. Each cartridge includes a connector that is mated to a corresponding connector in the testing rack, providing electrical contact between the wafer and the automated test equipment (ATE) system. The automated test equipment may be made up of multiple, independently operated test stations, where each test station is dedicated to a particular wafer cartridge slot in the handler. Therefore, the testing of multiple wafers can be done independently and simultaneously. The ATE system may be a stacked modular BIST tester, wherein a dedicated tester module is connected to each cartridge. The devices on the wafer are tested by running a test program on the ATE equipment which provides a variety of stimuli to the devices and measures and records the results. The cartridges are manually removed after testing is complete. The wafers can then be unloaded or left in the cartridges for additional test insertions. Manual insertion cartridge-based test cells are described in U.S. Pat. No. 6,340,895, “Wafer-level burn-in and test cartridge”, Frank Otto Uher et al, and in U.S. Pat. No. 6,580,283, “Wafer level burn-in and test methods”, Mark Charles Carbone et al.In the art, the stacked modular tester and stacked cartridge configuration has generally been utilized for burn in testing.        
There are several key disadvantages to this prior manual insertion cartridge based test cell approach. The cartridge must be designed to allow the probe card to move, thereby adding cost and complexity. The entire cartridge must be moved from the alignment station to the location where it connects to the test system, increasing the size and weight of the object that must be moved either manually or robotically. This design requires a contactor between the cartridge and test system that undergoes repeated insertions. Each time a new wafer is inserted the cartridge must be moved to the alignment station and then back to the testing location, requiring a cycling of the contactor. This adds cost to the contactor both from the need for a durable contactor and the need to periodically replace the contactor when its lifetime cycling specification is reached.
A multi-wafer test system that conserves horizontal floor space, is cost effective and efficient would be an important development.